There is required a heat-insulation film which is formed on a surface to improve a heat insulation efficiency and flame retardance. In Patent Document 1, a coating film is disclosed which has a high surface hardness and can prevent the surface from being damaged. The coating film is formed by dispersing hollow particles made of silica shells in a binder. By a wear resistance and high hardness of the hollow particles made of the silica shells, the wear resistance of a substrate on which the coating film is formed can improve. Additionally, the flame retardance can improve due to heat insulation properties of the hollow particles made of the silica shells.
In Patent Document 2, there is disclosed an internal combustion engine including a structural member in which a heat insulation performance improves. In the internal combustion engine of Patent Document 2, a heat-insulation material is disposed adjacent to an inner wall of an exhaust passage, and a high-temperature operative gas (an exhaust gas) flows along through channels made of the heat-insulation material. In the heat-insulation material, MSS (mesoporous silica sphere) particles having an average particle diameter of 0.1 to 3 μm are laminated in a state where the respective particles are densely bonded to one another via a bonding material. In the MSS particles, an infinite number of mesopores having an average pore diameter of 1 to 10 nm are formed.